I have made up the example below.
(1a) Today is very sunny. For the past two days, it has rained a lot.
My non-native English speaking friends think the tense used for "rain" is wrong. Their revised sentence is given below.
(1b) Today is very sunny. For the past two days, it rained a lot.
Which tense of "to rain" is correct? Thank you very much for your time and help.